With constant evolution of communication wireless network technologies from 2G Global Systems for Mobile Communications (GSM) to 3G Wideband Code Division Multiple Access (WCDMA) systems, and to 3G Long Term Evolution (LTE) systems, network deployment of operators also needs to meet user requirements necessarily, and systems of multiple standards may coexist. Currently, wireless network functions of the operators are defined generally as follows: the 2G GSM systems are mainly configured to carry voices, the 3G WCDMA systems are mainly configured to carry packet domain services, session services and video services, and the 3G LTE systems focus on carrying ultra high speed packet services.
Therefore, inter-system mobility of the 2G GSM system and the 3G WCDMA system is of great importance according to the current network deployment. In addition, mobility management of the 3G LTE systems, e.g. switching to hotspot regions of the LTE systems will become important in the near future.
A switching process resulted from the above inter-system mobility management needs to measure a target system and a target carrier frequency during a preliminary switching preparation stage, so as to execute a switching decision accurately.
A compressed mode plays an important role in the inter-carrier frequency measurement and inter-system measurement. When the compressed mode is applied, a terminal is able to measure a non-serving carrier frequency and carrier frequencies of other systems without any need to be configured with double receivers. When a terminal, which is configured with only one receiver, moves from a 3G WCDMA system to an area covered by a 2G GSM system only, the inter-system measurement can only be performed using the compressed mode. Similarly, the compressed mode can be also applied in a case that a terminal enters and exits an area covered by multiple carrier frequencies of a 3G WCDMA system. Under the compressed mode, a terminal can measure another non-serving carrier frequency without losing any data transmitted on a serving carrier frequency.
The compressed mode is defined as a transmission mode. In this way, data transmission will be compressed in the time domain to generate a transmission gap, in which a receiver of a terminal can be tuned to another carrier frequency to perform measurement.
The transmission gap is described and determined by a “transmission gap pattern sequence”. Each set of “transmission gap pattern sequence” is uniquely identified by a “transmission gap pattern sequence identifier” and can be applied to only one “transmission gap pattern sequence measurement purpose”, i.e. one of the measurement purposes such as “Frequency-Division Duplexing (FDD) measurement”/“Time-Division Duplexing (TDD) measurement”/“GSM carrier frequency Received Signal Strength Indication (RSSI) measurement”/“initial identification of GSM Base Station Identity Code (BSIC)”/“reconfirmation of GSM Base Station Identity Code (BSIC) identification”/“multi-carrier frequency measurement” and “Evolved Universal Terrestrial Radio Access (E-UTRA) measurement” etc.
As shown in FIG. 1, each set of “transmission gap pattern sequence” comprises two kinds of alternate “transmission gap patterns”, i.e. “transmission gap pattern 1” and “transmission gap pattern 2”. Each kind of transmission gap pattern provides one or two transmission gaps within one “transmission gap pattern length”. In addition, each set of “transmission gap pattern sequence” also comprises a transmission gap Connection Frame Number (CFN) indicating the start/stop time of the compressed mode, and repetition times of the transmission gap pattern, etc. These parameters are all determined according to the “transmission gap pattern sequence measurement purpose”.
Considering accelerating the switching process and improving switching reliability, especially in the area where the radio signal quality is deteriorating rapidly, the inter-carrier and inter-system measurement needs to be completed quickly. In other words, the later the compressed mode is started, the better it is; and the shorter the duration time of the compressed mode is, the better it is, so as to improve system capability and user throughput. Therefore, it is considered that the compressed mode between a terminal and a node B is controlled by the terminal. The terminal judges that the radio signal quality of a current serving cell is bad, and inter-carrier frequency and inter-system measurement may need to be performed to make preparation for switching to an adjacent cell among carrier frequencies/systems, then the terminal starts the compressed mode and notifies the node B.
A compressed mode can be controlled by a terminal or/a base station (node B) to be started/stopped rapidly within a short period of time. However, problems may exist if the terminal is in a macro-diversity state (i.e. radio links exist between the terminal and two or more Universal Terrestrial Radio Access Network (UTRAN) access points at the same time). In the schematic diagrams illustrating networking structures as shown in FIG. 2 and FIG. 3, a radio link is established between the terminal and node B1 (NodeB1) under RNC1, and between the terminal and node B2 (NodeB2) under RNC1 at the same time in the scenario of FIG. 2; a radio link is established between the terminal and NodeB1 under RNC1, and between the terminal and NodeB2 under RNC2 at the same time in the scenario of FIG. 3. In such cases, starting/stopping a compressed mode is controlled by the terminal or NodeB1 while NodeB2 fails to learn the execution state of the compressed mode. Therefore, the compressed mode cannot be executed by NodeB2 and the terminal synchronously, and the compressed mode of the terminal cannot be operated normally, thus influencing the service quality of the terminal and the performance of the system.